In high volume manufacturing processes such as semiconductor device fabrication and solar cell manufacturing, there is a continuing need to improve substrate throughput. This places a demand to improve throughput for processes including ion implantation. In one example, as the size of silicon wafers continues to scale upwardly, ion sources having a much larger current output are needed to meet required wafer throughput.
Beamline ion implantation apparatus may employ indirectly heated cathode (IHC) ion sources or other sources in which an elongated aperture is used to extract an ion beam. One manner of achieving higher ion current for implantation is to employ an ion source having a longer extraction aperture for a given ion density so that a greater total current may be extracted from the ion source. Dipole magnets are used to generate magnetic fields to enhance plasma density in conventional ion sources such as IHC sources that have more compact extraction optics where the extraction aperture is typically less than about 100 mm in length. However, such dipole magnets do not generate desired beam uniformity in elongated ion sources where the extraction aperture is longer. In view of the above, it will be appreciated that there is a need to improve ion implantation apparatus, and in particular to develop ion source technology to increase the current generating capability in the ion source while maintaining acceptable ion beam properties.